Each of magneto-electric conversion elements such as a Hall element and a magnetic resistance (MR) element is an element for detecting a magnetic field and converting it into an electrical signal. The MR element is constituted of an alloy thin film mainly containing a ferromagnetic metal such as Ni or Fe formed on an integrated circuit chip. The alloy thin film constitutes four resistors of a Wheatstone bridge circuit. A reduction in the resistance values of two of the four resistors due to change of external field intensity causes a mid-point potential difference of the bridge circuit to occur. A magnetic sensor using a magneto-electric conversion element such as the Hall element or the MR element is disclosed in, e.g., PTL 1. PTL 1 discloses, in FIG. 1, a magnetic sensor circuit having a Hall element, a switch circuit for switching between a method for applying a power supply voltage VDD to the Hall element and a Hall voltage extraction method, an amplifier unit including first and second amplifier circuits for amplifying the output from the switch circuit, and a comparison unit for comparing the outputs of the two amplifier circuits through capacitors. The two amplifier circuits and comparison unit are intermittently driven. Further, PTL 1 discloses, in FIGS. 7 and 8 and paragraphs [0072] to [0076], that a power-on signal POW for intermittent control is generated by a control circuit in the magnetic sensor circuit.